A key technical problem in radio and microwave communication is interference suppression and cancellation. In an existing communications system, a transmit antenna logically used for transmitting a signal and a receive antenna logically used for receiving a signal may physically be a same antenna or different antennas. However, although the transmit antenna and the receive antenna are physically different antennas, the transmit antenna and the receive antenna are generally relatively close to each other because a physical cabling layout of the communications system is limited. Therefore, in a same communications system, a transmitting link generally interferes with a receiving link, and a signal transmitted by the transmitting link is an interference signal for the receiving link.
In a conventional technology, to reduce interference of a transmitting link to a receiving link in a communications system, an interference cancellation unit is generally disposed to process a signal received by the receiving link, to cancel an interference signal included in the signal. As shown in FIG. 1, a power divider may divide a transmitted signal into two signals. One signal is sent by a transmit antenna to a remote end for transmission, and the other signal is inputted into an interference cancellation unit as a cancellation reference signal. As shown in FIG. 2, an interference cancellation unit subtracts a cancellation reference signal from a signal received by a receive antenna, to obtain a received signal without interference. Therefore, a signal-to-noise ratio is increased.
However, it is found by means of research that the interference signal cancellation apparatus and method in the conventional technology have at least the following problem: When performing interference cancellation on a received signal according to a cancellation reference signal, an interference cancellation unit generally needs to perform a parameter adjustment operation such as time shift, phase shift, or attenuation on the cancellation reference signal, so that the cancellation reference signal corresponds to a component of an interference signal in the received signal. Therefore, before a received signal without interference is obtained, because an operation process of time shift, phase shift, or attenuation is performed on the cancellation reference signal (that is, a power of the interference signal may firstly increase and then decrease), the interference signal in the received signal obtained by a receiver may be strengthened. Because an excessively strong interference signal may increase a bit error rate, communication is interrupted and consequently a communications system becomes unstable.